Scroll compressor and air conditioner

ABSTRACT

A scroll compressor comprises an operating state detection part ( 27 ) detecting an operating state, a variable-speed motor ( 28 ), a control part ( 26 ) and an unloading mechanism ( 12 ) serving as capacity control means. The control part ( 26 ) controls operation of the unloading mechanism ( 12 ) and the rotational frequency of the motor ( 28 ) in response to the operating state detected by the operating state detection part ( 27 ). An air conditioner comprises the aforementioned scroll compressor, a condenser ( 23 ), an expansion valve ( 24 ) and an evaporator ( 25 ).

TECHNICAL FIELD

The present invention relates to a scroll compressor and an airconditioner, and more specifically, it relates to a scroll compressorand an air conditioner capable of controlling switching between unloadedoperation and full-loaded operation, controlling the capacity ofrefrigerant injection and controlling the rotational frequency of amotor on the basis of a result of detection of the operating state.

BACKGROUND ART

FIG. 17 shows an exemplary conventional refrigerant compressor. Thiscompressor is disclosed in Japanese Patent Laying-Open No. 11-182479(1999).

As shown in FIG. 17, the refrigerant compressor comprises a closedcontainer 63 having a fixed scroll 56 and a rocking scroll (not shown)built therein. A cylinder 53 is formed on an end of the closed container63. A piston control valve 51 and a compression spring 52 are set in thecylinder 53.

The cylinder 53 is further provided with a first passage 60communicating with an intermediate pressure space 59, a second passage61 communicating with a suction pressure space 57 and a third passage 62communicating with a discharge pressure space 58 through a dischargeport 55. A back pressure space 54 of the piston control valve 51communicates with the third passage 62.

In the compressor having the aforementioned structure, the pistoncontrol valve 51 moves in response to the difference between a suctionpressure (Ps) and a discharge pressure (Pd) for a refrigerant toopen/close the first passage 60. Thus, the operating state of thecompressor is switched between operation (full-loaded operation) closingthe first passage 60 for attaining discharge capacity of 100% andoperation (unloaded operation) opening the first passage 60 for reducingthe discharge capacity.

The aforementioned compressor, automatically controlling switchingbetween unloaded operation and full-loaded operation in response to thepressure condition in the compressor, has the following problem. Thisproblem is now described with reference to FIG. 18. FIG. 18 illustratesthe relation between a condensing temperature (Tc), an evaporatingtemperature (Te) and an operating pressure ratio (Pr).

When the evaporating temperature (Te) is low and the condensingtemperature (Tc) is high (the region shown by slanting lines in FIG. 18)while required refrigerating ability is small in a refrigerating cycle,for example, the aforementioned compressor is not subjected to unloadedoperation. This is because the suction pressure (Ps) for the refrigerantis reduced and the discharge pressure (Pd) is increased when theevaporating temperature (Te) is low and the condensing temperature (Tc)is high, to close the aforementioned first passage 60.

When not subjected to unloaded operation but operated with small abilityas described above, the compressor must unavoidably be operated at a lowpressure with difficulty in lubrication. In such low-speed operation,further, motor efficiency is lower than that in intermediate- orhigh-speed operation, and efficiency may be reduced due to leakage ofcompression gas in the compressor or the like.

As hereinabove described, the conventional compressor automaticallycontrols switching between unloaded operation and full-loaded operationwithout detecting the operating state. Therefore, the compressor cannotsometimes be properly and efficiently operated in response to theoperating state. This problem can also arise in an air conditionercomprising the aforementioned compressor.

DISCLOSURE OF INVENTION

The present invention has been proposed in order to solve theaforementioned problem. An object of the present invention is to providea scroll compressor and an air conditioner capable of selecting properand efficient operation in response to every operating state.

A scroll compressor according to the present invention has a movablescroll (2) and a fixed scroll (1) forming a compression chamber (40)compressing a refrigerant, and comprises a variable-speed motor (28),capacity control means (12, 35), an operating state detection part (27)and a control part (26). The variable-speed motor (28) drives themovable scroll (2). The capacity control means (12, 35) controls thecapacity of the scroll compressor by supplying the refrigerant into thecompression chamber (40) or bypassing the refrigerant from thecompression chamber (40) to a low-pressure side. The operating statedetection part (27) detects the operating state of the scrollcompressor. The control part (26) controls operation of the capacitycontrol means (12, 35) and the rotational frequency of the motor (28) inresponse to the operating state detected by the operating statedetection part (27).

The scroll compressor comprises the aforementioned operating statedetection part (27), so that the operating state of the scrollcompressor can be detected. Further, the scroll compressor comprises theaforementioned control part (26), so that the operation of the capacitycontrol means (12, 35) and the rotational frequency of the motor (28)can be controlled in response to the operating state of the scrollcompressor. Thus, proper and efficient operation can be selected underevery operating condition. The aforementioned operating state detectionpart (27) and control part (26) may be set not only in the compressorbut also in a refrigerating/air conditioner system.

In the scroll compressor according to the present invention, theoperating state detection part (27) preferably includes an operatingpressure ratio detection part detecting an operating pressure ratioindicating the value of the ratio of a suction pressure for therefrigerant to a discharge pressure for the refrigerant and a requiredability detection part detecting required ability in operation of thescroll compressor, and the control part (26) preferably controls theoperation of the capacity control means (12, 35) and the rotationalfrequency of the motor (28) in response to the aforementioned operatingpressure ratio and required ability.

The operating state detection part (27) has the operating pressuredetection part and the required ability detection part as hereinabovedescribed, whereby the operating state of the scroll compressor such asthe operating pressure ratio or the required ability can be detected.The control part (26) controls the operation of the capacity controlmeans (12, 35) and the rotational frequency of the motor (28) inresponse to the operating pressure ratio and the required abilitydetected in the aforementioned manner, so that the scroll compressor canbe operated in high efficiency under every operating condition.

In the scroll compressor according to the present invention, thecapacity control means (12, 35) preferably includes unloading means (12)for substantially delaying a compression starting point in thecompression chamber (40) and performing unloaded operation.

The capacity control means (12, 35) can be exemplified by the unloadingmeans (12). When the scroll compressor comprises the unloading means(12), the unloading means (12) can be intentionally operated in responseto the operating state of the scroll compressor for performing unloadedoperation. More specifically, the unloading means (12) can beintentionally operated for performing unloaded operation underconditions of a low evaporating temperature, a high condensingtemperature and small required refrigerating ability, for example. Thus,it is possible to avoid the general problem of low-speed operation withdifficulty in lubrication.

In the scroll compressor according to the present invention, thecapacity control means (12, 35) includes refrigerant injection means(35) for injecting the refrigerant into the compression chamber (40).

The capacity control means (12, 35) can alternatively be exemplified bythe refrigerant injection means (35). When the scroll compressorcomprises the refrigerant injection means (35), the injection means (35)can be properly operated in response to the operating state of thescroll compressor and the capacity of the scroll compressor can beincreased. Thus, the variable ability width of the scroll compressor canbe increased. When employing the refrigerant injection means (35) alongwith the aforementioned unloading means (12), the control part (26) cancontrol the operation of the unloading means (12) not to unnecessarilyoperate during injection of the refrigerant. Thus, it is possible toavoid such a situation that the injected refrigerant leaks into asuction pressure chamber and the quantity of circulation of therefrigerant cannot be sufficiently increased.

The scroll compressor according to the present invention preferablyfurther comprises a discharge port (19) discharging the compressedrefrigerant and a discharge valve (20) for opening/closing the dischargeport (19) and preventing the refrigerant from counterflow.

In unloaded operation, the scroll compressor is generally operated at alow speed. Therefore, discharge resistance of the refrigerant is soreduced that the refrigerant may flow backward in the discharge port(19). Such counterflow of the refrigerant can be prevented andcounterflow loss can be reduced by providing the discharge valve (20) inthe aforementioned manner. Thus, efficiency in low-speed operation canbe improved.

The scroll compressor according to the present invention preferablyfurther comprises a relief port (29) communicating with the compressionchamber (40) reaching the discharge pressure and a relief valve (31 a)opening/closing the relief port (29).

The scroll compressor is operated at a high speed in an unloaded stateunder conditions of a high evaporating temperature, a low condensingtemperature and large required refrigerating ability, for example. Whenthe scroll compressor is operated at a high speed, however, the flowrate of discharge gas may be increased to increase over-compressionloss. The refrigerant reaching the discharge pressure can-be properlydischarged to a high-pressure space by providing the relief port (29)and the relief valve (31 a) as described above. Thus, over-compressionloss can be reduced and operating efficiency can be improved.

In the scroll compressor according to the present invention, the movablescroll (2) and the fixed scroll (1) preferably have spiral bodies (41,42), and the tail end of one of the spiral bodies (41) preferablyextends toward a portion close to the tail end of the other spiral body(42).

When the scroll compressor has the so-called asymmetrical spiral bodiesas described above, unloading ports can be intensively provided on oneportion as elements forming an unloading mechanism and injection portscan also be intensively provided on one portion as elements of arefrigerant injection mechanism.

The scroll compressor according to the present invention preferablycomprises a suction pressure space (33) on the back surface of the fixedscroll (1).

When the suction pressure space (33) is provided on the back surface ofthe fixed scroll (2) as described above, no detour may be provided forreleasing the refrigerant to a low-pressure space in unloaded operationbut the unloading mechanism can be simplified.

An air conditioner according to the present invention comprises theaforementioned scroll compressor. Throughout the specification, the airconditioner is defined as including not only a cooling/heating systembut also a refrigerator.

When the air conditioner comprises the scroll compressor having theaforementioned structure, high-efficiency operation is enabled in everyoperating state.

The air conditioner according to the present invention is preferably theso-called multiple air conditioner including a compressor (37) having acompression element compressing a refrigerant and a plurality ofloading-side heat exchangers (25 a, 25 b, 25 c) condensing orevaporating the refrigerant, and comprises a variable-speed motor,capacity control means (12 a), an operating state detection part (39)and a control part (38). The variable-speed motor drives the compressionelement. The capacity control means (12 a) supplies the refrigerant tothe compression element or extracts the refrigerant from the compressionelement thereby controlling the capacity of the compressor. Theoperating state detection part (39) detects the operating state of theair conditioner. The control part (38) controls the operation of thecapacity control means (12 a) and the rotational frequency of the motorin response to the operating state detected by the operating statedetection part (39). The aforementioned loading-side heat exchanger canbe exemplified by an indoor unit (evaporator or condenser) of an airconditioner, for example.

When the air conditioner comprises the operating state detection part(39) as described above, the operating state of the air conditioner canbe detected. The control part (38) can control the operation of thecapacity control means (12 a) and the rotational frequency of the motoron the basis of the result of the detected operating state. Thus, whenthe difference between an evaporating temperature and a condensingtemperature is so small that high ability is necessary, for example, thecontrol part (38) can operate the capacity control means (12 a) forperforming unloaded operation and rotating the motor at a high speed,thereby reducing over-compression loss. When the difference between theevaporating temperature and the condensing temperature is large and theability may be small, the control part (38) can perform full-loadedoperation without operating the capacity control means (12 a) and rotatethe motor at a low speed, thereby reducing counterflow loss(under-compression). Consequently, high-efficiency operation can beperformed under every operating condition. In heating operation with alow outside air temperature and a low evaporating temperature, forexample, the control part (38) can operate the capacity control means(12 a) for injecting a gas refrigerant and rotate the motor at a highspeed, thereby increasing the quantity of discharged refrigerant withoutextremely increasing the rotational frequency of the motor. In thiscase, reliability of the compressor can be improved. When adiabaticefficiency of the compressor is reduced and the temperature of thedischarged refrigerant is increased in low-speed operation of thecompressor, the control part (38) can operate the capacity control means(12 a) for injecting a liquid refrigerant, thereby reducing thetemperature of the discharged refrigerant. Thus, not only reduction ofthe life of the refrigerant or lubricating oil can be suppressed butalso operation of the air conditioner may not be stopped due to anincreased temperature of the discharged refrigerant.

In the air conditioner according to the present invention, the operatingstate detection part (39) preferably includes an operating pressureratio detection part detecting an operating pressure ratio indicatingthe value of the ratio of a suction pressure for the refrigerant to adischarge pressure for the refrigerant in the aforementioned compressorand a required ability detection part detecting required ability of theloading-side heat exchangers (25 a, 25 b, 25 c) in operation of the airconditioner, and the control part (38) preferably controls the operationof the capacity control means (12 a) and the rotational frequency of themotor in response to the aforementioned operating pressure ratio andrequired ability.

Thus, high-efficiency operation can be performed as described above bydetecting the operating state such as the operating pressure ratio orthe required ability and controlling the operation of the capacitycontrol means (12 a) and the rotational frequency of the motor on thebasis of the operating state.

In the air conditioner according to the present invention, the operatingstate detection part (39) includes a number detection part detecting thenumber of operated loading-side heat exchangers (25 a, 25 b, 25 c), forcontrolling the operation of the capacity control means (12 a) and therotational frequency of the motor also in consideration of the number ofthe operated loading-side heat exchangers.

In the multiple air conditioner, the number of the operated loading-sideheat exchangers (25 a, 25 b, 25 c) also influences the required abilityin addition to the relation between the evaporating temperature and thecondensing temperature. When the aforementioned number detection part isprovided, therefore, the operation of the capacity control means (12 a)and the rotational frequency of the motor can be controlled also inconsideration of the number of the operated loading-side heatexchangers. Thus, high-efficiency operation can be performed also whenthe temperature difference between the evaporating temperature and thecondensing temperature is small and all loading-side heat exchangers (25a, 25 b, 25 c) are operated or the temperature difference is large andthe loading-side heat exchangers are partially operated.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic block diagram of a scroll compressor according tothe present invention illustrated with a refrigerating cycle;

FIG. 2 is a sectional view taken along the line X—X in FIG. 1;

FIG. 3 illustrates exemplary opening angle ranges of an unloading port,a relief port, an injection port and a discharge port;

FIG. 4 illustrates the relation between operating temperature conditions(condensing temperature and evaporating temperature) and an operatingpressure ratio;

FIG. 5 illustrates the relation between a compressor efficiency ratioand the operating pressure ratio;

FIG. 6A illustrates the relation between pressure change of arefrigerant and an angle of rotation of a movable scroll under a lowoperating pressure ratio condition in an unloaded OFF state;

FIG. 6B illustrates the relation between pressure change of therefrigerant and the angle of rotation of the movable scroll under ageneral operating pressure ratio condition in the unloaded OFF state;

FIG. 6C illustrates the relation between pressure change of therefrigerant and the angle of rotation of the movable scroll under a highoperating pressure ratio condition in the unloaded OFF state;

FIG. 7A illustrates the relation between pressure change of therefrigerant and the angle of rotation of the movable scroll under a lowoperating pressure ratio condition in an unloaded ON state;

FIG. 7B illustrates the relation between pressure change of therefrigerant and the angle of rotation of the movable scroll under ageneral operating pressure ratio condition in the unloaded ON state;

FIG. 7C illustrates the relation between pressure change of therefrigerant and the angle of rotation of the movable scroll under a highoperating pressure ratio condition in the unloaded ON state;

FIG. 8 illustrates the relation between pressure change of therefrigerant and the angle of rotation of the movable scroll under thehigh operating pressure ratio condition in the unloaded ON stateprovided with a discharge valve;

FIG. 9 is a partially fragmented sectional view of the scroll compressorillustrated with a relief port and a relief valve;

FIG. 10 illustrates the relation between pressure change of therefrigerant and the angle of rotation of the movable scroll under ageneral operating pressure ratio condition in the unloaded ON stateprovided with and not provided with the relief valve;

FIG. 11 is a partially fragmented sectional view of the scrollcompressor employing a back space of a fixed scroll as a low-pressure(suction pressure) space;

FIG. 12 is a schematic block diagram of the scroll compressor comprisingan unloading mechanism and a refrigerant injection mechanism;

FIG. 13 is a schematic block diagram of an air conditioner according tothe present invention;

FIG. 14 illustrates the relation between a condensing temperature and anevaporating temperature;

FIG. 15 is a flow chart for illustrating exemplary operation of the airconditioner shown in FIG. 13;

FIG. 16 is a flow chart for illustrating exemplary operation of the airconditioner shown in FIG. 13 having a refrigerant injection mechanismadded thereto;

FIG. 17 is a partially fragmented sectional view of a conventionalrefrigerant compressor; and

FIG. 18 illustrates the relation between operating temperatureconditions (condensing temperature and evaporating temperature) and anoperating pressure ratio.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are now described with reference toFIGS. 1 to 16. FIG. 1 is a schematic block diagram of a scrollcompressor according to an embodiment of the present invention.

As shown in FIG. 1, the scroll compressor according to the presentinvention comprises a casing 18, a fixed scroll 1, a movable scroll 2,an unloading mechanism, a discharge pipe (high-pressure line) 14, acontrol part 26, an operating state detection part 27 and a motor 28.

The fixed scroll 1, the movable scroll 2 and the motor 28 are built inthe casing 18. The fixed scroll 1 has a discharge port 19 discharging arefrigerant, an unloading port 4 opened in unloaded operation, a valvehole 5, a bypass path 6, a bypass valve 7, a coil spring 8, a lid member9, an a operating pressure chamber 11, a discharge valve 20, a valvespring 21 and a valve guard 22.

The bypass path 6 makes a low-pressure space 3 storing an uncompressedrefrigerant communicate with a compression chamber 40 and extracts therefrigerant from the compression chamber 40 into the low-pressure space3 in unloaded operation, for substantially delaying a compressionstarting point for the refrigerant. The bypass valve 7 is set in theoperating pressure chamber 11 for opening/closing the unloading port 4.

The lid member 9 closes an opening of the valve hole 5. The lid member 9receives a joint pipe 16 therethrough. The discharge valve 20,opening/closing the discharge port 19, opens to discharge therefrigerant reaching a discharge pressure into a discharge dome 10.

The motor 28 drives the movable scroll 2 through a crank shaft (notshown). The compression chamber 40 is formed between the movable scroll2 and the fixed scroll 1, for compressing the refrigerant therein.

The unloading mechanism includes the unloading port 4, the valve hole 5,the bypass path 6, the bypass valve 7, the coil spring 8, the lid member9, the operating pressure chamber 11, an unloaded operation valve 12, anoperating pressure line 15, the joint pipe 16 and a capillary tube 17.The scroll compressor can be subjected to unloaded operation by openingthe unloaded operation valve 12 and operating the unloading mechanism.

The discharge pipe (high-pressure line) 14 discharges the refrigerant ofa high pressure discharged into the discharge dome 10 from the casing18. The discharged refrigerant passes through a low-pressure line 13through a condenser 23, an expansion valve 24 and an evaporator 25, forexample, to be fed into the scroll compressor again.

The operating state detection part 27 detects the operating state of thescroll compressor. More specifically, the operating state detection part27 has an operating pressure ratio detection part and a required abilitydetection part and detects an operating pressure ratio Pr of the scrollcompressor and required ability in operation of the scroll compressor.

The operating pressure ratio Pr is the ratio (Pd/Ps) of a suctionpressure Ps for the refrigerant to a discharge pressure Pd for therefrigerant. The discharge pressure Pd can be substantially replacedwith a condensing pressure Pc in a refrigerant condensing process whilethe suction pressure Ps can be substantially replaced with anevaporating pressure Pe in a refrigerant evaporating process, and hencethe operating pressure ratio Pr can be calculated by detecting thepressures Pc and Pe. The pressures Pc and Pe are obtained on the basisof a condensing temperature Tc and an evaporating temperature Te, forexample.

When an apparatus comprising the scroll compressor is an airconditioner, for example, the required ability of the scroll compressorcan be detected on the basis of temperature conditions such as a suctionair temperature of an indoor unit, an indoor set temperature, indoorhumidity and the outside air temperature.

The rotational frequency of the motor 28, which is a variable-speedmotor driven by an inverter, can be increased/decreased at need.

The control part 26 controls operation of the unloading mechanism andthe rotational frequency of the motor 28 on the basis of the result ofdetection by the operating state detection part 27. More specifically,the control part 26 opens the unloaded operation valve 12 for performingunloaded operation when determining that unloaded operation is proper,and increases/decreases the rotational frequency of the motor 28 whenfurther capacity control is necessary in this operating state.

FIG. 2 shows a sectional structure taken along the line X—X in FIG. 1.As shown in FIG. 2, the fixed scroll 1 and the movable scroll 2 havespiral bodies 41 and 42 respectively, so that a plurality of compressionchambers 40 are formed between the spiral bodies 41 and 42. Referring toFIG. 2, the spiral bodies 41 and 42 are asymmetrical and the tail end ofthe spiral body 41 is located in the vicinity of the tail end of thespiral body 42.

The fixed scroll 1 is provided with an injection port 30 and a reliefport 29 in addition to the aforementioned discharge port 19 andunloading port 4, as shown in FIG. 2.

The injection port 30, employed for injecting a gas refrigerant or aliquid refrigerant into the compression chambers 40, can increase thecapacity of the scroll compressor by injecting the gas refrigerant andreduce the temperature of the discharged refrigerant by injecting theliquid refrigerant.

The scroll compressor has the so-called asymmetrical spiral bodies 41and 42 as described above, whereby the unloading port 4 and theinjection port 30 can be intensively provided on one portion. In otherwords, two compression chambers 40 starting compression with deviationof about 180° C. can successively communicate with the ports 4 and 30 bysimply providing these ports 4 and 30 on one portion.

FIG. 3 illustrates communication angle ranges of the unloading port 4,the discharge port 19, the relief port 29 and the injection port 30 withreference to the communication chambers 40. Referring to FIG. 3, αdenotes the communication angle range of the unloading port 4, β denotesthe communication angle range of the relief port 29, γ denotes thecommunication angle range of the discharge port 19, and δ denotes thecommunication angle range of the injection port 30.

Characteristic operation of the scroll compressor having theaforementioned structure is now described.

First, the operating state detection part 27 detects the operating stateof the scroll compressor. More specifically, the operating pressureratio detection part of the operating state detection part 27 detectsthe operating pressure ratio Pr, and the required ability detection partof the operating state detection part 27 detects the required ability ofthe scroll compressor.

In order to detect the operating pressure ratio Pr, the operating statedetection part 27 detects the condensing temperature Tc and theevaporating temperature Te with a temperature sensor or the like andobtains the condensing pressure Pc and the evaporating pressure Pe onthe basis of these values. Then the operating state detection part 27calculates the operating pressure ratio Pr from these pressure values.

FIG. 4 shows exemplary relation between the operating pressure ratio Pr,the condensing temperature Tc and the evaporating temperature Te.Referring to FIG. 4, the refrigerant is prepared from R22 (CHCIF2). FIG.5 shows the relation between an efficiency ratio η* of the scrollcompressor and the operating pressure ratio Pr. The aforementionedefficiency ratio η* indicates an efficiency ratio with reference to apressure ratio maximizing efficiency in full-loaded operation.

It is understood from FIG. 4 that the operating pressure ratio Pr varieswith the combination of the condensing temperature Tc and theevaporating temperature Te. It is also understood from FIG. 5 thatwhether full-loaded operation or unloaded operation is optimum dependson the operating pressure ratio Pr. This is because the optimum pressureratio depends on the winding angles of the scrolls 1 and 2, the positionof the discharge port 19 and the ratio of the volume of the compressionchambers 40 for starting compression to that for starting communicatingwith the discharge port 19.

Thus, it is understood that full-loaded operation and unloaded operationare preferably switched in response to the value of the operatingpressure ratio Pr in order to keep high efficiency of the scrollcompressor.

Referring to FIGS. 4 and 5, an unloaded/full-load operation switchingtarget operating pressure ratio Pro forming the standard for switchingunloaded operation and full-loaded operation may be set to 2.2 to 3.This pressure ratio Pro, conceivably varying with the type of the usedrefrigerant and the application of a refrigerator/air conditioner, ispreviously obtained in response to the type of the used refrigerant andthe application.

The control part 26 compares the pressure ratio Pr calculated inoperation of the scroll compressor with the aforementioned pressureratio Pro for selecting full-loaded operation in principle when thepressure ratio Pr is greater than the pressure ratio Pro while selectingunloaded operation in principle when the pressure ratio Pr is less thanthe pressure ratio Pro. Alternatively, unloaded operation may beselected when it is predicted from the indoor temperature, thecondensing temperature Tc and the evaporating temperature Te varyingfrom hour to hour that the pressure ratio Pr lowers below the pressureratio Pro before long.

Thus, over-compression loss can be reduced under low operating pressureratio conditions and counterflow loss can be reduced under highoperating pressure ratio conditions as shown in FIGS. 6A to 7C.

The unloaded operation valve 12 is kept closed in order to performfull-loaded operation, while the control part 26 opens the unloadedoperation valve 12 in order to perform unloaded operation.

However, it may be rather advantageous to select unloaded operation alsowhen the pressure ratio Pr is greater than the pressure ratio Pro. Morespecifically, unloaded operation is preferably selected when theevaporating temperature Te is low, the condensing temperature Tc is high(the operating pressure ratio Pr is high) and the required ability issmall, for example.

In this case, the aforementioned required ability detection part detectsthe required ability on the basis of temperature conditions etc. inoperation of the scroll compressor, and hence the control part 26intentionally opens the unloaded operation valve 12 on the basis of theresult of this detection. Thus, it is possible to avoid full-loadedlow-speed operation causing difficulty in lubrication and improvereliability of the scroll compressor.

Also in the case of selecting unloaded operation when the operatingpressure ratio Pr is high, the required ability can be attained byproperly adjusting the rotational frequency of the motor 28 by thecontrol part 26.

In the case of performing unloaded operation when the operating pressureratio Pr is high, however, under-compression (counterflow loss)increases as compared with the case of full-loaded operation, as shownin FIGS. 6C and 7C.

Such counterflow loss can be reduced by providing the discharge valve 20as shown in FIG. 1 thereby preventing the refrigerant from counterflowin unloaded operation (see FIG. 8). Consequently, efficiency inlow-speed operation can be improved.

FIG. 9 is a sectional view of the scroll compressor illustrated with arelief valve mechanism 31. As shown in FIG. 9, the scroll compressor isprovided with the relief port 29 communicating with the compressionchamber 40 reaching the discharge pressure and a relief valve 31 aopening/closing the relief port 29. A valve guard 32 is provided on therelief valve 3 a, and the relief valve 31 a as well as the valve guard32 are mounted on the fixed scroll 1 with a bolt 43.

When the relief valve 31 a is provided in the aforementioned manner, therefrigerant reaching the discharge pressure can be discharged into thedischarge dome 10 through the relief port 29 upon high-speed operationin an unload state, for example, thereby reducing over-compression lossas shown in FIGS. 7A and 10. This also can effectively contribute toimprovement of the efficiency of the scroll compressor.

As shown in FIG. 11, a suction pressure space 33 is preferably providedon the back surface of the fixed scroll 1. Thus, the refrigerant can bereleased into the suction pressure space 33 through the bypass path 6 ain unloaded operation, and no detour may be provided for releasing therefrigerant into a low-pressure space but the unloading mechanism can besimplified.

FIG. 12 is a schematic block diagram of the scroll compressor having theaforementioned structure, to which a refrigerant injection mechanism isfurther added.

As shown in FIG. 12, the scroll compressor comprises an injection port30 for injecting the refrigerant into the compression chamber 40, aninjection pipe 35 for guiding the refrigerant to the injection port 30and a refrigerant supply part 44 supplying the refrigerant to theinjection pipe 35.

When the scroll compressor comprises the refrigerant injection mechanismin the aforementioned manner, the variable ability width can be furtherincreased than the above case. If required ability cannot be attained byrotating the motor 28 at a high speed in full-loaded operation, thecontrol part 26 can drive the refrigerant supply part 44 for supplyingthe gas refrigerant into the compression chamber 40. Thus, the abilityof the scroll compressor can be improved.

When injecting the refrigerant, the control part 26 keeps the unloadedoperation valve 12 closed. Thus, the injected refrigerant can beinhibited from leaking into a suction compression chamber.

The operating state detection part 27 is set to also detect thetemperature of the discharged refrigerant from the temperature of thedischarge pipe 14. When the temperature of the refrigerant isexcessively increased, the control part 26 can drive the refrigerantsupply part 44 for supplying the liquid refrigerant into the compressionchamber 40. Thus, not only reduction of the life of the refrigerant orlubricating oil can be suppressed but also operation stoppage of theapparatus resulting from increase of the temperature of the refrigerantcan be avoided.

While the scroll compressor according to the present invention has beendescribed, the inventive scroll compressor may simply comprise at leasteither the refrigerant injection mechanism for supplying the refrigerantinto the compression chamber 40 or the unloading mechanism extractingthe refrigerant from the compression chamber 40 toward the low-pressureside as capacity control means of the scroll compressor.

An air conditioner according to the present invention is now describedwith reference to FIGS. 13 to 16. FIG. 13 schematically illustrates thestructure of the air conditioner according to the present invention.

The air conditioner shown in FIG. 13 is the so-called multiple airconditioner, and comprises a plurality of loading-side heat exchangers.More specifically, the air conditioner comprises a condenser 23, anexpansion valve 24, evaporators 25 a to 25 c serving as the loading-sideheat exchangers, a compressor 37, an unloaded operation valve 12 a, afour-way switching valve 36, an operating state detection part 39 and acontrol part 38.

The compressor 37, which may be a variable capacity compressor, ispreferably a scroll compressor. The compressor 37 has a compressionelement compressing a refrigerant, a variable-speed motor driving thecompression element and an unloading mechanism serving as capacitycontrol means. A refrigerant injection mechanism may be provided as thecapacity control means, similarly to the case of the aforementionedscroll compressor.

The operating state detection part 39 detects the operating state of theair conditioner. Similarly to the case of the aforementioned scrollcompressor, this operating state detection part 39 includes an operatingpressure ratio detection part detecting an operating pressure ratio of adischarge pressure for a refrigerant to a suction pressure for therefrigerant in the compressor 37, a required ability detection partdetecting required ability of the evaporators 25 a to 25 c in operationof the air conditioner, and a number detection part detecting the numberof operated ones of the evaporators 25 a to 25 c. The operating pressureratio and the required ability are detected similarly to the case of theaforementioned scroll compressor.

The control part 38 controls operation of the unloading mechanism andthe rotational frequency of a motor in response to the operatingpressure ratio, the required ability and the number of the operated onesof the evaporators 25 a to 25 c.

When the air conditioner comprises the operating state detection part 39and the control part 38 as described above, the operation of theunloading mechanism and the rotational frequency of the motor can becontrolled on the basis of the result of detection of the operatingstate of the air conditioner.

Thus, when the difference between the evaporating temperature of therefrigerant in the evaporators 25 a to 26 c and the condensingtemperature of the refrigerant in the condenser 23 is small and largeability is required, for example, the control part 38 opens the unloadedoperation valve 12 a for performing unloaded operation while rotatingthe motor at a high speed. Thus, over-compression loss can be reduced.

When the aforementioned temperature difference is small and the abilitymay be small, the control part 38 closes the unloaded operation valve 12a for performing full-loaded operation while rotating the motor at a lowspeed. Thus, counterflow loss can be reduced.

Thus, high-efficiency operation can be performed also under conditionsshown by regions 2 and 4 in FIG. 14.

When the air conditioner comprises a refrigerant injection mechanism(not shown) as the capacity control means of the compressor, the controlpart 38 can operate the refrigerant injection mechanism for injecting agas refrigerant and rotating the motor at a high speed in heatingoperation with a low outside air temperature and a low evaporatingtemperature, for example. In this case, the quantity of dischargedrefrigerant can be increased without extremely increasing the rotationalfrequency of the motor, and reliability of the compressor can beimproved.

When adiabatic efficiency of the compressor is reduced and thetemperature of the discharged refrigerant is increased in low-speedoperation of the compressor, the temperature of the dischargedrefrigerant can be reduced by operating the refrigerant injectionmechanism for injecting a liquid refrigerant. Thus, not only reductionof the life of the refrigerant or lubricating oil can be suppressed butalso operation of the air conditioner may not be stopped due to anincreased temperature of the discharged refrigerant.

In the multiple air conditioner shown in FIG. 13, the number of theoperated loading-side heat exchangers also influences the requiredability, in addition to the relation between the evaporating temperatureand the condensing temperature. When the air conditioner is providedwith the number detection part as described above, the operation of theunloading mechanism and the rotational frequency of the motor can becontrolled also in consideration of the number of the operatedloading-side heat exchangers.

Thus, high-efficiency operation can be performed also when thetemperature difference between the evaporating temperature and thecondensing temperature is small and all evaporators 25 a to 25 c areoperated or the temperature difference is large and the evaporators 25 ato 25 c are partially operated, for example.

The compressor 37 may be provided with a discharge valve and a reliefvalve, similarly to the case of the aforementioned scroll compressor.

Exemplary operation of the air conditioner according to the presentinvention is now described with reference to FIGS. 15 and 16. FIG. 15 isa flow chart for illustrating exemplary operation (cooling operation) ofthe air conditioner shown in FIG. 13. FIG. 16 is a flow chart forillustrating exemplary operation of the air conditioner shown in FIG.13, to which the refrigerant injection mechanism is added.

Referring to FIG. 15, the operating state detection part 39 detects thecondensing temperature Tc in the condenser (outdoor unit) 23 and theevaporating temperature Te in the evaporators (indoor units) 25 a to 25c. At this time, the operating state detection part 39 also detects theoperating frequency f of the compressor 37 and the current ability ofeach indoor unit.

At a step S2, the operating state detection part 39 obtains arefrigerant condensing pressure Pc (substantially equal to a dischargepressure Pd) and a refrigerant evaporating pressure Pe (substantiallyequal to a suction pressure Ps) from the condensing temperature Tc andthe evaporating temperature Te, thereby calculating an operatingpressure ratio Pr (Pc/Pe).

At a step S3, the control part 38 compares the aforementioned operatingpressure ratio Pr with an unloaded operation/full-loaded operationswitching target operating pressure ratio Pro previously input as data.

When the pressure ratio Pr is less than the pressure ratio Pro, thecontrol part 38 opens the unloaded operation valve 12 a at a step S4,for performing unloaded operation.

At a step S5, the operating state detection part 39 detects whether ornot the ability of the evaporators (indoor units) 25 a to 25 c issufficient in the aforementioned unloaded operation. The operatingfrequency f of the compressor 37 is kept as such at a step S7 if theability is proper, while the control part 38 increases theaforementioned operating frequency f at a step S8 if the ability isinsufficient, or reduces the aforementioned operating frequency f at astep S7 if the ability is excessive.

After increasing the operating frequency f at the step S8, the operatingstate detection part 39 determines whether or not the operatingfrequency f is at the maximum operable value and the ability of theevaporators (indoor units) 25 a to 25 c is insufficient at a step S9. Ifthe ability is insufficient, the control part 38 closes the unloadedoperation valve 12 a at a step S13 for performing full-loaded operation.If the ability is sufficient, the aforementioned operating frequency fis kept as such at a step S10.

After reducing the aforementioned operating frequency f at the step S7,the operating state detection part 39 determines whether or not theoperating frequency f is at the minimum operable value and the abilityof the evaporators (indoor units) 25 a to 25 c is excessive at a stepS11. The control part 38 stops the compressor 37 at a step S12 if theability is excessive, while the aforementioned operating frequency f iskept as such at the step S10 if the ability is not excessive.

If the pressure ratio Pr is in excess of the pressure ratio Pro at thestep S3, the process advances to a step S13 so that the control part 38keeps the unloaded operation valve 12 a closed for performingfull-loaded operation.

After performing full-loaded operation in the aforementioned manner, theoperating state detection part 39 determines whether or not the abilityof the evaporators (indoor units) 25 a to 25 c is sufficient at a stepS14. The operating frequency f of the compressor 37 is kept as such at astep S15 if the ability is proper, while the control part 38 increasesthe aforementioned operating frequency f at a step S19 if the ability isinsufficient, or reduces the aforementioned operating frequency f at astep S16 if the ability is excessive.

After reducing the operating frequency f at the step S16, the operatingstate detection part 39 determines whether or not the operatingfrequency f is at the minimum operable value and the ability of theevaporators (indoor units) 25 a to 25 c is excessive at a step S17. Theprocess returns to the step S4 if the ability is excessive so that thecontrol part 38 opens the unloaded operation valve 12 a for performingunloaded operation, while the aforementioned operating frequency f iskept as such at a step S18 if the ability is not excessive.

After increasing the operating frequency f at the step S19, theoperating state detection part 39 determines whether or not theoperating frequency f is at the maximum operable value and the abilityof the evaporators (indoor units) 25 a to 25 c is insufficient at a stepS20. The operating frequency f of the compressor 37 is kept at themaximum value at a step S22 if the ability is insufficient, while theaforementioned operating frequency f is kept at a step S21 if theability is not insufficient.

When adjusting the ability, unloaded operation and full-loaded operationmay be frequently switched to result in a possibility of abnormalvibration. Such hunting can be prevented by increasing an ability changeratio Qmax/Qmin of minimum operating frequency ability Qmin to maximumoperating frequency ability Qmax under a full-loaded (or unloaded) statebeyond an ability change ratio Qf/Qu of unloaded operation ability Qu tofull-loaded operation ability Qf at the same operating frequency.

Exemplary operation of the air conditioner provided with the refrigerantinjection mechanism is now described.

Referring to FIG. 16, operation up to a step S21 is similar to thatdescribed above and hence redundant description is not repeated. Whenthe operating frequency f is at the maximum operable value and theability of the evaporators (indoor units) 25 a to 25 c is insufficientat a step S20, the control part 38 operates the refrigerant injectionmechanism at a step S22 for injecting the gas refrigerant into thecompression element in the compressor 37.

After the aforementioned injection, the operating state detection part39 determines whether or not the ability of the evaporators (indoorunits) 25 a to 25 c is sufficient at a step S23. The operating frequencyf of the compressor 37 is kept as such at a step S24 if the ability isproper, the aforementioned operating frequency is kept at the maximumvalue at a step S25 if the ability is insufficient, while the controlpart 38 reduces the aforementioned operating frequency f at a step S26if the ability is excessive.

The air conditioner can be efficiently operated in every operating statedue to the aforementioned operation control.

The air conditioner shown in FIG. 13, comprising a single compressor,may alternatively comprise a plurality of compressors. When the airconditioner comprises a plurality of compressors, an inverter compressorprovided with the aforementioned capacity control mechanism may becombined with another type of compressor (a compressor provided with aconstant speed capacity control mechanism or a compressor provided witha constant speed-constant capacity compressor, for example).

According to the present invention, as hereinabove described, a scrollcompressor and an air conditioner capable of performing high-efficiencyoperation in every operating state and having a large variable abilitywidth as well as high reliability can be obtained. The air conditionercan be inhibited from a complicated system connecting a number ofminiature compressors in parallel with each other, and the cost can bereduced.

The present invention is effectively applicable to a scroll compressorand an air conditioner.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A scroll compressor having a movable scroll and afixed scroll forming a compression chamber compressing a refrigerant,said scroll compressor comprising: a variable-speed motor driving saidmovable scroll; capacity control means controlling the capacity of saidscroll compressor by supplying said refrigerant into said compressionchamber or bypassing said refrigerant from said compression chamber to alow-pressure side; an operating state detection part detecting theoperating state of said scroll compressor; and a control partcontrolling operation of said capacity control means and the rotationalfrequency of said motor; wherein said operating state detection partincludes an operating pressure ratio detection part detecting anoperating pressure ratio indicating the value of the ratio of a suctionpressure for said refrigerant to a discharge pressure for saidrefrigerant and a required ability detection part detecting requiredability in operation of said scroll compressor, and wherein said controlpart controls operation of said capacity control means and therotational frequency of said motor in response to said operatingpressure ratio and said required ability.
 2. The scroll compressoraccording to claim 1, wherein said capacity control means includesunloading means for delaying a compression starting point in saidcompression chamber and performing unloaded operation.
 3. The scrollcompressor according to claim 1, wherein said capacity control meansincludes refrigerant injection means for injecting said refrigerant intosaid compression chamber.
 4. The scroll compressor according to claim 1,further comprising: a discharge port discharging compressed saidrefrigerant, and a discharge valve for opening/closing said dischargeport and preventing said refrigerant from counterflow.
 5. The scrollcompressor according to claim 1, further comprising: a relief portcommunicating with said compression chamber reaching a dischargepressure, and a relief valve opening/closing said relief port.
 6. Thescroll compressor according to claim 1, wherein said movable scroll andsaid fixed scroll have spiral bodies, and the tail end of one saidspiral body extends toward a portion close to the tail end of the othersaid spiral body.
 7. The scroll compressor according to claim 2,comprising a suction pressure space on the back surface of said fixedscroll.
 8. An air conditioner comprising the scroll compressor accordingto claim
 1. 9. An air conditioner including a compressor having acompression element compressing a refrigerant and a plurality ofloading-side heat exchangers condensing or evaporating said refrigerant,said air conditioner comprising: a variable-speed motor driving saidcompression element; capacity control means supplying said refrigerantto said compression element or extracting said refrigerant from saidcompression element thereby controlling the capacity of said compressor;an operating state detection part detecting the operating state of saidair conditioner; and a control part controlling operation of saidcapacity control means and the rotational frequency of said motor;wherein said operating state detection part includes an operatingpressure ratio detection part detecting an operating pressure ratioindicating the value of the ratio of a suction pressure for saidrefrigerant to a discharge pressure for said refrigerant in saidcompressor and a required ability detection part detecting requiredability of said loading-side heat exchangers in operation of said airconditioner, and wherein said control part controls operation of saidcapacity control means and the rotational frequency of said motor inresponse to said operating pressure ratio and said required ability. 10.The air conditioner according to claim 9, wherein said operating statedetection part further includes a number detection part detecting thenumber of operated said loading-side heat exchangers, for controllingoperation of said capacity control means and the rotational frequency ofsaid motor also in consideration of the number of said operatedloading-side heat exchangers.